I Know Dino: The Big Dinosaur Podcast

I Know Dino Podcast Show Notes: Majungasaurus (Episode 124)

In our 124th episode, we got a chance to talk to Ariel Marcy, a biologist, PhD student, tutor, and creator of the educational game “Go Extinct!” through her startup STEAM Galaxy. Get “Go Extinct!” at steamgalaxy.com and follow Ariel’s progress on her new games at aemarcy.com

Episode 124 is also about Majungasaurus, a large Abelisaurid that lived in the Cretaceous in what is now Madagascar.

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The dinosaur of the day: Majungasaurus

Name means Majunga dome

Type species (only species): Majungasaurus crenatissimus

Species name means “most notched” and refers to all the serrations on its teeth

For a while it was called Majungatholus, and now that’s considered to be a junior synonym

Charles Depéret, a French paleontologist, described the first theropod fossils from Madagascar in 1896 (two teeth, a claw, and some vertebrae that a French army officer had found). These fossils were classified as Megalosaurus (wastebasket taxon), and named a new species: Megalosaurus crenatissimus. Later Depéret reassigned these fossils to Dryptosaurus, another taxon not well known

The fossils were found in 1895 by French scientists who were with the French military on a expedition to secure the island from the British

Over the next 100 years French collectors found more fragments in the Mahajana Province in Madagascar. René Lavocat described theropod teeth in 1955, and those teeth matched the teeth that Depéret had described earlier, but he also described a strongly curved jaw bone that was different from Megalosaurus and Dryptosaurus. Based on this dentary, Lavocat made a new genus Majungasaurus

Majungasaurus is an older spelling of Mahajanga

In 1979, Hans-Dieter Sues and Philippe Taquet described a dome-shaped skull fragment as Majungatholus atopus, a pachycephalosaur (the first one described in the southern hemisphere)

In 1993, a team from the State University of New York at Stony Brook and the University of Antananarivo started the Mahajanga Basin Project, which were a number of expeditions to the Mahajanga Province. On the first expedition they found hundreds of theropod teeth that looked like Majungasaurus. Over the course of seven expeditions they found tens of thousands of fossils, many which were new species

In 1996 scientists found a complete theropod skull, which had a dome-shaped horn on the top (similar to the dome that Sues and Taquet described as Majungatholus atopus). In 1998, Majungatholus was redescribed as an abelisaurid (instead of a pachycephalosaur). Majungasaurus crenatissimus was named before Majungatholus atopus, but scientists thought that what was desscribed as Majungasaurus was too fragmentary to assign to the same species as this skull. Over the next 10 years more skulls (less complete) were found, as well as partial juvenile and adult skeletons, and isolated bones and thousands of shed teeth. All these together form a nearly complete skeleton, though most of the forelimbs, pelvis, and tip of the tail are not known.

In 2007, all those bones were part of a monograph, made up of 7 scientific papers on all aspects of Majungasaurus (from material found between 1993 and 2001). The dentary that Lavocat was reevaluated and found to be characteristic for the species. The name Majungasaurus replaced Majungatholus.

David Krause, from Stony Brook University and who was part of the Mahajanga Basin Project, decided to give back to the local community in Madagascar who helped him throughout the years on his expeditions. They told him they wanted education for their children, and need to hire a teach, which cost $500 per year. He and his team raised the money for the teacher’s salary, and in 1998 Krause founded the Madagascar Ankizy Fund (named after the Malagasy word for children). They’ve built schools and provided health care.

Krause helped find the Majungasaurus skull in 1996

One of the best studied theropods from the southern hemisphere

Seems to be more closely related to abelisaurids from India than abelisaurids from South America or Africa

Bipedal, with a short snout

About 20-23 ft (6-7 m) long, though there are estimates, based on fragments, of some being as long as 26 ft (8 m)

Weighed about 2,400 lb (1,100 kg), though larger ones may have weighed up to 3,300 lb (1,500 kg)

Had a long tail to help balance

Had short forelimbs, with stocky hind limbs

Had four digits on each hand, though it was thought to only have two digits and no claws. The specimen studied had no pits and grooves where claws would normally be attached, and its finger bones were fused together, so the hand was immobile

A 2012 study of another specimen found the four digits were very short and inflexible, and had small claws on the second and third digits

Feet had three digits, and the first digit was smaller and didn’t touch the ground

Had a strong, muscular neck

Had a wide, short skull, and had a rounded, dome-like horn on the roof of the skull, which was originally thought to be a pachycephalosaur dome

Skull had a rough texture

Had nasal bones that were thick and fused together

Horn on the top of the skull was probably covered with keratin

CT scans found that the nasal structure and horn on the top of the head had hollow sinus cavities, possibly to reduce weight

Majungasaurus probably competed with each other, using the fused nasals and the horn on top of its head, though how is unclear (the horn’s hollow cavity means it was not strong enough to use for fighting, and probably was more for display). Majungasaurus had some variation in the horns, but no evidence of sexual dimorphism

As Majungasaurus grew and became older, its skull got taller and more robust, and the skull bones were more fused and eye sockets became smaller. This shows juveniles and adults probably had different diets

Michael D’Emic’s research shows it was one of the slowest growing theropods, based on lines of arrested growth on the bones. Took Majungasaurus 20 years to mature

A CT scan of a complete skull allowed scientists to reconstruct the brain and inner ear structure. The brain was small relative to its body size, but was similar to other non-coelurosaurian theropods. One difference is compared to other theropods, Majungasaurus had a smaller floccus (which controls balance coordination). Because of this, it probably didn’t move its head quickly to look for and go after prey. Also its inner hear shows it held its head straight and horizontal to the ground. Probably went after slower prey, like large sauropods

Apex predator, that preyed on Rapetosaurus (sauropod)

Had more teeth in upper and lower jaws, compared to other abelisaurids

May have bitten prey and held on until its prey stopped fighting (bite and hold approach)

Had a flexible lower jaw, may have helped prevent fractures when holding onto its prey

Teeth curved on the front edge but were straighter in the back, possibly to hold teeth in place when biting (instead of slicing prey)

Probably specialized in hunting sauropods (stocky legs would have helped it bite and hold), and didn’t need to be as fast to go after slower sauropods

Majungasaurus tooth marks have been found on Rapetosaurus (so it ate them, though not clear if it killed them)

One of the few dinosaurs with direct evidence of cannibalism

In 2007 scientists published about some finds that showed Majungasaurus practiced cannibalism. Majungsaurus bones were found with tooth marks that looked the same as tooth marks found on sauropods in the area.

Many of the bite marks on Majungasaurus were on limb bones that were only accessible during lethal combat, according to Scott Sampson in Dinosaur Odyssey

Majungasaurus is the only large known theropod in the area, so that probably means they fed on each other. Majungsaurus is the only non-avian theropod proven to be cannibalistic (though there is evidence of cannibalism in other species)

Not clear if Majungasaurus hunted each other or just scavenged carcasses (though Komodo dragons sometimes kill each other in feeding frenzies of carcasses)

Scientists have been able to reconstruct Majunasaurus’ respiratory system. Had air sacs like modern birds that allowed for a “flow through ventilation”, meaning the air flows through the lungs one way (air inhaled is never mixed with air exhaled, which is efficient)

This shows that the split between ceratosaurs (which led to Majungsaurus) and the tetanurans (which led to birds) happened early on with theropods. This common avian respiratory system would have evolved before the split, and helps show that birds are dinosaurs

In 2007 a report described four Majungasaurus pathologies, based on the remains of 21 individuals. No wounds found on the skull, but one had a broken and healed toe bone. Another had a bony growth on the underside of a back vertebra, probably from cartilage conversion during development. Another had abnormal growth on its tail vertebra, probably from ossification of a ligament. Another had abnormalities on five large tail verebrae. Three were fused together at multiple points, making a solid bony mass. No sign of other vertebrae after the fifth one, so the tail was shorter than most (about 10 vertebrae short). Could be from severe trauma that resulted in losing the tip of the tail and then infection, or the infection came first and part of the tail fell off. First example of tail truncation found in a non-avian theropod

Majungasaurus lived in a semi-arid climate on a coastal flood plain. Sea levels were rising. Madagascar was an island even when Majungasaurus.

Had wet and dry seasons. Each year, animals that died from lack of water were then swept away by water during the wet season and buried (led to lots of preserved fossils)

Other animals that lived at the same time and place include fish, frogs, lizards, snakes, crocodylomorphs, and some mammals and birds, as well as the noasaurid Masiakasaurus, two titanosaurs, including Rapetosaurus. Also possibly the dromaeosaurid Rahonavis

Part of Indominus rex’s DNA in Jurassic World is Majungasaurus

Can see Majungasaurus in the fifth episode of the miniseries When Dinosaurs Ruled, hosted by Jeff Goldblum

Can also see Majungasaurus in the first episode of Jurassic Fight Club (talking about its cannibalism)

Both shows called it Majungatholus

Can see Majungasaurus in BBC’s Planet Dinosaur (and it’s called Majungasaurus)

Fun fact: Coprolite can preserve fragile specimens (kind of like amber) allowing paleontologists to study organism that the couldn’t find in a typical geological formation.

For those who may prefer reading, see below for the full transcript of our interview with Ariel Marcy: